The Inertia Contributing Writer
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A screenshot of Kelly Slater’s Instagram post, showing Richenberg’s biomimetic fins. Photo: Instagram


The Inertia

In a freesurf session at pumping Pipeline last month, Kelly Slater packed a Backdoor barrel, emerged, then boosted a hefty alley oop. (Coincidentally, John John Florence did almost the same thing during the same session).

Slater’s wave was impressive enough to make it one of this winter’s most recognized. But his performance might not be the most interesting thing about it. Rather, that might be the rear quad fins that can be seen during Slater’s lofty rotation.

Stuck into his board was a set that might just revolutionize fin design by copying nature. Those fins mimic whale flippers and bird wings. That is, the fins flex from the leading edge to the trailing edge, as well as from the base to the tip, as conventional fins do.

The result is that the fin carries more speed through turns, courtesy of how it snaps back into place after flexing. “It responds in the most critical part of the turn. You can feel the fin flex and accelerate,” says the fin’s designer, Randy Richenberg, the 61-year-old owner of a small surfboard business in Florida. His two maiden designs, both based on foil shapes found in nature, could change everything we think we know about our thrusters, quads, singles and twins.

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If it’s any indication how well the fins work, Slater has been testing them for two years. Though he’s notoriously cagey about his equipment, the Champ has posted Richenberg’s fins on his Instagram account with the words, “Testing, tesing.” And in addition to his barrel-to-air combo, and several other epic freesurfs caught on video, Slater rode Richenberg’s fins in the Gold Coast World Championship Tour event last year. They were also screwed into his backup boards (and maybe the board he rode) during the Billabong Pipeline Masters in December. As perhaps the most innovative surfer alive, it says something that Slater puts his faith in these designs.

Former CT surfers Brad Gerlach and Shea Lopez, along with shapers Matt Biolos and Maurice Cole, have tried them, too, apparently with favorable results. Gerlach, who coaches CT surfer Conner Coffin, says he’s going to suggest that Coffin try them out. “They feel like they flow through the water with an extra pop to them,” Gerlach says. “They allow you to S-turn and flow through flat sections as well as give you the feeling that you can fit the board into a smaller spot in the wave without force.” Gerlach says the fins would be equally suited to any surfboard shape, from shortboards to fishes, guns and beyond.

Richenberg isn’t the first or only person to create ridged fins, or fins that flex from the leading to trailing edges. Notably, Kiwi surfboard shaper Roy Stuart has designed fins with bumped leading edges, as we’ve discussed. But the acceptance by Slater, Gerlach, and other surfers marks the first time that fins with these characteristics have found their way into top surfers’ fin plugs, and at the highest levels of competition.

Richenberg has been developing two prototype fin types, both engineered to mimic structures that evolution perfected over millions of years. This type of design, called biomimicry, has given rise to many innovations in engineering. One example from the sports world is a swimsuit created by Speedo: its fabric resembles the denticles that make up shark skin and help the fish swim faster.

“We take designs that work well in nature and apply them to manmade designs to enhance performance,” Richenberg says. “These aren’t some strange shape. They’re fundamental designs based on traditional foils.”

The fin type Slater rode during his alley oop, that Richenberg calls Bioflex, is constructed of carbon fiber and kevlar. The leading edge is stiffer than the trailing edge, so the flexibility increases as the fin tapers from front to back.

The second model is more distinctive looking, characterized by a series of bumps on the leading edge, which are modeled after the tubercules on humpback whales’ flippers. Richenberg calls that model the Nova, a shorthand for humpbacks’ scientific name, Megaptera novaeangliae. The bumps are believed to be responsible for the preternatural agility of humpbacks, a skill no animal that is 50 feet long and weighs 40 tons should have. Yet, thanks to their flippers, humpbacks can swim in a circle five feet in diameter. The tubercules act like a claw in the water, maintaining grip “at sharper angles and tighter corners, even at slow speeds,” according to a Harvard University study.

As Richenberg puts it: “Evolution doesn’t do things because it looks cool.”

Richenberg’s Bioflex design. Photo: Randy Richenberg

The story of how these fins came into being is even more incredible considering their inventor. Richenberg owns a small business building mostly custom surfboards in Edgewater, Florida. Before hitting upon the idea for these fins, he wasn’t an inventor, or marketer, just a surfer of 50 years and a diver and fisherman who’s seen plenty of fins performing in their natural environment. “My interest piqued when someone introduced me to biomimicry,” he says. “I wanted to apply those same disciplines to make the equipment we ride better.” Richenberg got the fins to Slater through mutual friends, and has watched in delight as they’ve appeared in Slater’s equipment around the world.

Ready to buy a pair? Sorry, but the fins probably won’t be available until this spring, when Richenberg hopes to have them on the market. Right now he’s figuring out the manufacturing process and how to bring them to the retail market.